Bioacoustics of Elasmopus tubar

Description: based on male, 6.6 mm, UMAR-PERA-230. Head: short, 1/4 shorter than the two first segments of pereon; anterior head lobe grossly subtruncate, inferior head lobe short and nearly straight. Eyes: grape shape, pigment dark brown, width representing approximately 1/4 the length of head. Antenna 1: 2/5 the length of the body, first article of peduncle approximately 1/5 longer than second article and width subequal, length of third article 2/5 the length of first article; accessory flagellum with one article. Antenna 2: 3/5 shorter than antenna 1, articles 4–5 the same length; first article of flagellum is 1/3 the length of the fifth article of peduncle. Pereon: body length 3/5 longer than the antenna 1; dorsally smooth; color off-white in alcohol. Ventral margin of the coxae 2–4 with sparse long setae, formula for coxae 2–4: 4–3–1; coxae 5–6 with one and two short robust setae respectively. Gnathopod 1 with long simple setae external view, inner surface of propodus and carpus with numerous plumose setae; propodus 2/3 longer than the dactyl; propodus piriform, palm margin minutely denticulate, outer margin of palm with elongated simple setae and short robust setae, with inferior lateral short robust setae, and one robust seta at angle of the palm stronger and longer than the those of the palm margin. Gnathopod 2: longer piriform propodus, dactyl thin and elongated, propodus of gnathopod 2 approximately 1/3 longer than the dactyl; anterodistal margin of propodus with stridulation hump; oblique palm slightly convex with abundant and long plumose setae; palm margin with triangular setose hump near dactylar hinge, promptly a concave excavation with plumose setae, then mediofacial ridge-hump semi-hidden by setae. Pereopods 1–5: Merus and propodus of pereopod 1 the same length; basis of pereopod 2 1/2 longer than the merus; basis of pereopod 3 subquadrate; basis of pereopod 4 subrectangular; basis and merus of pereopod 4 the same length, posterodistal lobe of merus of pereopod 4 bicuspidate; basis of the pereopod 5 is semicircular, with posterodistal margin serrate; basis of the pereopod 5 1/2 wider than the merus; basis of the pereopods 3–5 without short simple setae. Pleon: epimera shorter with respect to general line of the body; ventral margin bearing only some short robust setae, formula for epimera 1–3 is 1:0, 2:1–2–2, 3:1–1–2–2–1; epimeron 3 lightly convex on posterior edge, posteroventral angle irregularly denticulated. Uropod 3: peduncle is 1/3 shorter than the outer ramous; outer ramous is 1/5 longer and wider than the inner ramous; inner ramous bearing one proximally short robust seta and two medial short robust setae; outer margin of outer ramous with two cluster of medial robust setae and one proximal robust seta; mediodistal margin of peduncle with four short robust setae, outer angle of peduncle with three short robust setae and inner angle with two short robust setae. Telson deeply cleft, lobes approximately 1/5 longer than the width, lobes slightly excavated or nearly truncate, apices armed with one plumose seta and three robust setae, lateral longest robust seta and decreasing abruptly in length toward the inner short robust setae. Female: based on female, 3.9 mm, UMAR-PERA-230. Gnathopod 1 like the male; but with shorter and scarce setae; outer angle of carpus without a long robust seta. Gnathopod 2 is like Gnathopod 1 for female; but with two short robust setae at inner angle of the palm. Coxa 1 widening gradually toward distal margin; anterodistal margin rounded and projected forward; coxa 2 suboblong, gradually narrow toward distal margin; coxa 3 subquadrate and anterodistally round; posterolateral margin of coxa 4 is emarginated, the emargination is 2/3 the total length posterolateral margin; ventral margin of the coxae 1–3 with long simple setae, the formula is 6–4–4; coxae 5–6 with short robust setae, the formula is 1–2; coxa 7 widening on posterior margin. Formula for epimera 1–3: 1:0, 2:1, 3:1–1–1. Posterodistal lobe of merus of pereopod 4 not bicuspidate. Uropod 3 with inner margin of inner ramous bearing one medial short robust seta, outer margin of outer ramous with two cluster medial short robust setae; mediodistal margin of peduncle of uropod 3 with two short robust setae, distal angles of peduncle with two robust setae at each. Telson deeply cleft, apices armed with one plumose seta and two robust setae, longest lateral spine is 3/4 longer than the inner robust setae. Taxonomic comments: the male from the Gulf of Tehuantepec presents some differences with E. tubar male from Cabo San Lucas, for details see Table 2 . The specimen revised by Barnard (1979) is possibly a preadult male, because of some characters described by Barnard (1979) such as the telson is similar to the female of Elasmopus tubar from the Gulf of Tehuantepec. Elasmopus tubar from the Gulf of Tehuantepec has an accessory flagellum with one article, while that from Cabo San Lucas is described with two articles. The formula of robust setae on ventral margin for the epimera 1–3 in E. tubar from the Gulf of Tehuantepec is 1:0, 2:1–2–2, 3:1–1–2–2–1, while that from Cabo San Lucas is 1:1–1–2, 2:1–1–1–1, 3:1–1–2–2–1–1. The posteroventral angle of epimeron 3 of E . tubar from the Cabo San Lucas has a very small tooth and sinus, while that from Gulf of Tehuantepec is irregularly denticulated. The posterior margin of epimeron 3 in E. tubar from Cabo San Lucas bears weak acclivities, each one with short simple setae, while that from Gulf of Tehuantepec has weak acclivities without simple setae. The distal margin of peduncle of uropod 3 in E. tubar from Cabo San Lucas has three medial short robust setae, while that from Gulf of Tehuantepec has four medial short robust setae. Elasmopus tubar from Cabo San Lucas has four short robust setae on outer angle of peduncle of uropod 3, while that from Gulf of Tehuantepec has only three. Telson of E. tubar from Cabo San Lucas has two robust setae and one simple apical seta, while the form of Gulf of Tehuantepec has three robust setae and one plumose apical seta. The lateral margins of each lobe of telson in E. tubar from the Cabo San Lucas have one plumose seta, while in the form of Gulf of Tehuantepec it is absent.